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CH 14: Olfaction
Terms in this set (56)
the sense of smell
the sense of taste
sniffing in and perceiving odors through our nostrils, which occurs when we are smelling something that is in the air
perceiving odors through the mouth while breathing and chewing; this is what gives us the experience of flavor
the translation of a chemical stimulus into the sensation of an odor percept; for example, 'the cake has a chocolate odor'
a molecule that is defined by its physiochemical characteristics, which are capable of being translated by the nervous system into the perception of smell
a narrow space at the back of the nose into which air flows and where the olfactory epithelium is located
a secretory mucous membrane in the human nose whose primary function is to detect odorants in inhaled air; located on both sides of the upper portion of the nasal cavity and olfactory clefts, the olfactory epithelium contains three types of cells: olfactory sensory neurons, basal cells, and supporting cells
The asymmetry characterizing the intake of air by the two nostrils, which corresponds to differing sensitivity to odorants between the two nostrils. Nasal dominance alternates nostrils throughout the day, but there is no predictability about when the nostrils alternate.
one of the three types of cells in the olfactory epithelium; provide metabolic and physical support for the olfactory sensory neurons
One of the three types of cells in the olfactory epithelium; the precursor cells to olfactory sensory neurons.
olfactory sensory neuron (OSN)
One of three cell types—the main one—in the olfactory epithelium; small neurons located beneath a mucous layer in the epithelium. The cilia on the OSN dendrites contain the receptor sites for odorant molecules.
Any of the hairlike protrusions on the dendrites of olfactory sensory neurons. The receptor sites for odorant molecules are on the cilia, which are the first structures involved in olfactory signal transduction.
odorant receptor (OR)
the region on the cilia of olfactory sensory neurons where odorant molecules bind
any of the spherical conglomerates containing the incoming axons of the olfactory sensory neurons; each OSN converges onto two (one medial, one lateral)
The blueberry-sized extension of the brain just above the nose, where olfactory information is first processed; there are two, one in each brain hemisphere, corresponding to the right and left nostrils
A bony structure riddled with tiny holes that separates the nose from the brain at the level of the eyebrows; the axons from the olfactory sensory neurons pass through the holes of this to enter the brain
the total inability to smell, most often resulting from sinus illness or head trauma
the first cranial nerve. the axons of the olfactory sensory neurons bundle together after passing through the cribriform plate to form this, which conducts impulses from the olfactory epithelium in the nose to the olfactory bulb; also called cranial nerve I
referring to the same side of the body (or brain)
The first layer of cells surrounding the glomeruli. They are a mixture of excitatory and inhibitory cells and respond to a wide range of odorants. The selectivity of neurons to specific odorants increases in a gradient fro the surface of the olfactory bulb to the deeper layers.
The next layer of cells after the juxtaglomerular neurons. They respond to fewer odorants than the juxtaglomerular cells, but more than neurons at the deepest layer of cells.
The deepest layer of neurons in the olfactory bulb. Each mitral cell responds only to a few specific odorants.
Like mitral cells, granular cells are at the deepest level of the olfactory bulb. They comprise an extensive network of inhibitory neurons, integrate input from all the earlier projections, and are thought to be the basis of specific odorant identification.
The bundle of axons of the mitral and tufted cells within the olfactory bulb that sends odor information to the primary olfactory cortex.
primary olfactory cortex/ piriform cortex
The neural area where olfactory information is first processed. It comprises the amygdala, parahippocampal gyrus, and interconnected areas; and it interacts closely with the entorhinal cortex.
The conjoined regions of the amygdala and hippocampus, which are key structures in the limbic system. This complex is critically involved in the unique emotional and associative properties of olfactory cognition.
A phylogenetically old cortical region that provides the major sensory association input into the hippocampus. The entorhinal cortex also receives direct projections from olfactory regions.
The group of neural structures that includes the olfactory cortex, the amygdala, the hippocampus, the piriform cortex, and the entorhinal cortex; involved in many aspects of emotion and memory; olfaction is unique among the senses for its direct connection to this
The fifth cranial nerve, which transmits information about the "feel" of an odorant (e.g., mint feels cool, cinnamon feels warm), as well as pain and irritation sensations (e.g., ammonia feels burning).
The current dominant biochemical theory for how chemicals come to be perceived as specific odors; contends that different scents—as a function of the fit between odorant shape to OR shape—activate different arrays of olfactory receptors in the olfactory epithelia. These various arrays produce specific firing patterns of neurons in the olfactory bulb, which then determine the particular scent we perceive.
An alternative to shape-pattern theory for describing how olfaction works; proposes that every odorant has a different vibrational frequency, and that molecules that produce the same vibrational frequencies will smell the same.
the inability to smell one specific compound amid otherwise normal smell perception
Isomers (molecules that can exist in different structural forms) in which the spatial arrangements of the atoms are mirror-image rotations of one another, like a right and left hand.
Competition between the two nostrils for odor perception. When a different scent is presented to each nostril simultaneously, we perceive each scent to be alternating back and forth with the other, and not a blend of the two scents.
The olfactory equivalent of "white noise" or the color white. When at least 30 odorants of equal intensity that span olfactory physiochemical and psychological (perceptual) space are mixed, they produce a resultant odor percept that is the same as every other mixture of 30 odorants meeting the span and equivalent intensity criteria, even though the various mixtures do not share any common odorants.
the science of defining quantitative relationships between physical and psychological (subjective) events
A psychophysical method for determining the concentration of a stimulus required for detection at the threshold level; an example of a method of limits. A stimulus (e.g., odorant) is presented in an ascending concentration sequence until detection is indicated, and then the concentration is shifted to a descending sequence until the response changes to "no detection." This ascending and descending sequence is typically repeated several times, and the concentrations at which reversals occur are averaged to determine the threshold detection level of that odorant for a given individual. Also called reverse staircase method.
A test in which a participant is given three odorants to smell, of which two are the same and one is different. The participant is required to state which is the odd odor out. Typically, the order in which the three odorants are given (e.g., same, same, different; different, same, same; same, different, same) is manipulated and the test is repeated several times for greater accuracy.
The inability to name an odor, even though it is very familiar. Contrary to the tip-of-the-tongue phenomenon, one has no lexical access to the name of the odor, such as first letter, rhyme, number of syllables, and so on, when in this state. This is an example of how language and olfactory perception are deeply disconnected.
G-protein coupled receptor
any of the class of receptors that are present on the surface of olfactory sensory neurons; all are characterized by a common structural feature of seven membrane spanning helices
The biochemical phenomenon, occurring after continual exposure to an odorant, whereby receptors stop responding to an odorant and detection ceases.
The reduction in detection of one odorant following exposure to a prior odorant; presumed to occur because the components of the odors (for odorants) in question share one or more olfactory receptors for their transduction, but the order in which odorants are presented also plays a role
The psychological process by which, after long-term exposure to an odor, one no longer has the ability to detect that odor or has very diminished detection ability.
The liking dimension of odor perception, typically measured with scales pertaining to an odorant's perceived pleasantness, familiarity, and intensity
orbitofrontal cortex (OFC)
The part of the frontal lobe of the cortex that lies behind the bone (orbit) containing the eyes; responsible for the conscious experience of olfaction, as well as the integration of pleasure and displeasure from food; and it has been referred to as the secondary olfactory cortex and the secondary taste cortex; also involved in many other functions, and it is critical for assigning affective value to stimuli—in other words, determining hedonic meaning.
learned fast aversion
the avoidance of a novel flavor after it has been paired with gastric illness; the smell, not the taste, of the substance is key for this response in humans
main olfactory bulb
The rounded extension of the brain just above the nose that is the first region of the brain where smells are processed (distinguished in nonhuman animals)
accessory olfactory bulb
A neural structure found in nonhuman animals that is smaller than the main olfactory bulb and located behind it and that receives input from the vomeronasal organ
Found in nonhuman animals, it is a chemical-sensing organ at the base of the nasal cavity with a curved tubular shape; evolved to detect chemicals that cannot be processed by ORs, such as large and/or aqueous molecules, the types of molecules that constitute pheromones; also called Jacobsen's organ
A chemical emitted by one member of a species that triggers a physiological or behavioral response in another member of the same species. Pheromones are signals for chemical communication and do not need to have any smell.
The position that females of some species need to assume in order to be impregnated; involves the downward curving of the spinal column and exposure of the genitals
A pheromone that triggers an immediate behavioral response among conspecifics.
A pheromone that triggers a physiological (often hormonal) change among conspecifics. This effect usually involves prolonged pheromone exposure.
Any of various chemicals emitted by humans that are detected by the olfactory system and that may have some effect on the mood, behavior, hormonal status, and/or sexual arousal of other humans.
The manipulation of odors to influence, mood, performance, and well-being, as well as the physiological correlates of emotion such as heart rate, blood pressure, and sleep.
THIS SET IS OFTEN IN FOLDERS WITH...
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